FailureAnalyzer doesn't provide useful information for the "null" bean case

[snicoll]

As of 5.0, if you have a null bean, autowiring fails rather than injecting null. The bean is present in the bean factory but the context won't resolve it for you anymore.

This is the failure analysis you get on startup with such a bean:

***************************
APPLICATION FAILED TO START
***************************

Description:

Parameter 0 of constructor in com.example.demo.MyStuff required a bean of type 'java.lang.String' that could not be found.


Action:

Consider defining a bean of type 'java.lang.String' in your configuration.

We should try to extract some more information (perhaps that the bean is null now we know it's a special case?).

[dsyer]

N.B. I found that I can set --debug to see the full exception. It doesn't help in this case because the exception message doesn't mention the null bean - it just insists that there are none.

[2018-06-20 09:07:38.701] - 27477 FINE [main] --- org.springframework.boot.diagnostics.LoggingFailureAnalysisReporter: Application failed to start due to an exception
org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'java.lang.String' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoMatchingBeanFound(DefaultListableBeanFactory.java:1509)
...

Maybe the log hint about --debug could mention that full stack traces are available that way? Currently it just says:

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.

[vahundos]

It can be something like this?

package org.springframework.boot.diagnostics.analyzer;

public class NullBeanInjectionFailureAnalyzer
		extends AbstractInjectionFailureAnalyzer<UnsatisfiedDependencyException>
		implements BeanFactoryAware {

	private ConfigurableBeanFactory beanFactory;

	@Override
	public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
		Assert.isInstanceOf(ConfigurableBeanFactory.class, beanFactory);
		this.beanFactory = (ConfigurableBeanFactory) beanFactory;
	}

	@Override
	protected FailureAnalysis analyze(Throwable rootFailure,
                                UnsatisfiedDependencyException cause, String description) {
		Class<?> parameterType = cause.getInjectionPoint()
				.getMethodParameter().getParameterType();
		try {
			beanFactory.getBean(parameterType);
		} catch (BeanNotOfRequiredTypeException e) {
			return new FailureAnalysis(String.format("Bean named '%s' with required type '%s' was found," +
					" but actually it is '%s'", e.getBeanName(), e.getRequiredType().getName(),
					e.getActualType().getName()),
					String.format("Check bean definition for bean named '%s'", e.getBeanName()), e);
		}
		return null;
	}
}

[snicoll]

@vahundos sorry I missed that. We already had a failure analyzer for this, see 6e749ef for more details.